Sterilizers are widely used to sterilize articles in medical and dental offices, hospitals, clinics, nursing homes, laboratories and other facilities to sterilize heat and moisture stable reusable articles, including dental handpieces. Sterilizers typically employ a steam filled sterilizer chamber for containing the article to be sterilized and a heater located within the chamber for increasing the temperature and pressure inside the chamber to a point where the article is sterilized. Sterilizers have a door which is mounted to open and close relative to an opening of the sterilizer chamber so that the articles may be placed within the chamber to be sterilized and thereafter removed.
In a typical sterilization cycle for solid articles, the articles are sealed within the chamber of the sterilizer and steam is supplied to the chamber. The steam may either be provided from a separate steam producing chamber or by supplying water to the chamber and heating the chamber until the water evaporates. In either case, the chamber is provided with a heater to elevate the temperature in the chamber and cause an accompanying increase in pressure such that sterilization of the articles is effected. Further, the presence of steam in the chamber facilitates an increase in pressure therein whereby the temperature and time required for completing the sterilization process may be kept to a minimum.
Sterilizers have conduits for conveying water from the water reservoir to the sterilizer chamber at the beginning of the sterilization cycle and for venting steam from the chamber back to the reservoir after the articles have been sterilized. The returned steam from the chamber is condensed in the water reservoir for reuse in a subsequent cycle. Valves are fluidly connected to the conduits and are controlled so that the proper sequence of filling the chamber with water and venting the steam from the chamber back to the reservoir occurs during the sterilization cycle. Following the sterilizing and venting portions of the sterilization cycle, the door may be opened while additional heat is provided within the sterilizer chamber to dry the sterilized items during a drying portion of the cycle.
Typically, sterilizers have pre-programmed sterilization cycles which are selected by a user for the particular article to be sterilized. Each pre-programmed sterilization cycle has a set sterilization temperature set point, sterilization time, and drying time for the cycle. However, certain situations may occur where the parameters of the pre-programmed sterilization cycles do meet the particular sterilization requirements of a user. Either the articles do not get adequately sterilized due to insufficient sterilization temperature or sterilization time or the articles are still damp after the sterilization cycle due to insufficient drying time.
During the sterilization cycle, it is desirable to obtain an optimum saturated environment of steam within the sterilizing chamber. Oftentimes, however, as the water within the chamber is heated and evaporated into steam, there is residual air within the chamber that prevents this optimum saturated steam environment from being obtained.
Also, it is desirable to maintain the temperature within the chamber very dose to the sterilization temperature set point to assure that the articles are properly sterilized during the sterilization cycle. However, the temperature within the chamber is oftentimes difficult to accurately control and temperature sensors have not provided the degree of temperature sensing accuracy that may be desired to monitor and control the chamber temperature during the sterilization cycle.
During the venting process, the steam is vented back to the water reservoir at a fixed vent rent to reduce the pressure within the sterilizer. Under certain circumstances, the venting of the steam, and the associated drop in pressure within the sterilizer chamber, is too rapid for certain articles being sterilized and the articles become damaged or are otherwise detrimentally affected by the rapid drop in pressure within the chamber following sterilization.
Venting of the steam from the sterilizing chamber to the water reservoir oftentimes causes problems since the water reservoir may be unsealed to prevent a build up of pressure within the water reservoir resulting from the returned steam. A build up of pressure within the water reservoir, if not properly vented, may cause the water within the reservoir to be expelled from a filling portion of the reservoir. When the reservoir has an opening to vent the returned steam, the steam is vented within the housing of the sterilizer which increases moisture within the sterilizer. This may cause problems to mechanical and electrical components within the housing which may be sensitive to the increased levels of moisture over time.
Oftentimes, the door is opened when there is some residual pressure remaining in the chamber after the sterilization process, and opening of the door can create a noise at times which may startle those located near the sterilizer or may otherwise be a nuisance in certain environments.
Therefore, there is a need for a sterilizer which overcomes these and other shortcomings and drawbacks of sterilizers heretofore know.